ECU(engine control unit), OBD(on-board diagnostic)
the ability to display engine check codes was a concern of mine six months ago. At that time, not having a reader, I was prepared to purchase a reader/gage. These things aint cheap (the readers), even the most basic ones that don't show much more than the trouble code, ugh!
Anyways, I discovered Autozone was one of a number of places that would check the code for free which was good enough at the time. Still, I've been on the lookout for an inexpensive reader.
But if I had to spend a few extra $$$, the above mentioned ScanGaugeII and X-gauge catch my interest.